Arjen Luijendijk, Gerben Hagenaars, Roshanka Ranasinghe, Fedor Baart, Gennadii Donchyts, Stefan Aarninkhof. The State of the World’s Beaches. Scientific Reports 8, 6641 (2018)
Coastal zones constitute one of the most heavily populated and developed land zones in the world. Despite the utility and economic benefits that coasts provide, there is no reliable global-scale assessment of historical shoreline change trends. Here, via the use of freely available optical satellite images captured since 1984, in conjunction with sophisticated image interrogation and analysis methods, we present a global-scale assessment of the occurrence of sandy beaches and rates of shoreline change therein. Applying pixel-based supervised classification, we found that 31% of the world’s ice-free shoreline are sandy. The application of an automated shoreline detection method to the sandy shorelines thus identified resulted in a global dataset of shoreline change rates for the 33 year period 1984–2016. Analysis of the satellite derived shoreline data indicates that 24% of the world’s sandy beaches are eroding at rates exceeding 0.5 m/yr, while 28% are accreting and 48% are stable. The majority of the sandy shorelines in marine protected areas are eroding, raising cause for serious concern.
Posted in Sea Level
Tagged sea level
“The Pacific nation of Tuvalu—long seen as a prime candidate to disappear as climate change forces up sea levels—is actually growing in size, new research shows.” click here
“the dramatic impacts of climate change felt on coastlines and people across the Pacific are still anecdotal” see discussion here
Michino Hisabayashi, John Rogan & Arthur Elmes. Quantifying shoreline change in Funafuti Atoll, Tuvalu using a time series of Quickbird, Worldview and Landsat data Journal GIScience & Remote Sensing Volume 55, 2018 Issue 3
Funafuti Atoll, Tuvalu is located in the southwestern Pacific Ocean, which has experienced some of the highest rates of global sea-level rise over the past 60 years. Atoll islands are low-lying accumulations of reef-derived sediment that provide the only habitable land in Tuvalu, and are considered vulnerable to the myriad possible impacts of climate change, especially sea-level rise. This study examines the shoreline change of twenty-eight islands in Funafuti Atoll between 2005 and 2015 using 0.65 m QuickBird, 0.46 m WorldView-2, and 0.31 m WorldView-3 imagery using an image segmentation and decision tree classification. Shoreline change estimates are compared to previous study that used a visual interpretation approach. The feasibility of estimating island area with Landsat-8 Operational Land Imager (OLI) data is explored using CLASlite software. Results indicate a 0.13% (0.35 ha) decrease in net island area over the study time period, with 13 islands decreasing in area and 15 islands increasing in area. Substantial decreases in island area occurred on the islands of Fuagea, Tefala and Vasafua, which coincides with the timing of Cyclone Pam in March, 2015. Comparison between the WorldView-2 shoreline maps and those created from Landstat-8 indicate that the estimates tend to be in higher agreement for islands that have an area > 0.5 ha, a compact shape, and no built structures. Ten islands had > 90% agreement, with percent disagreements ranging from 2.78 to 100%. The methods and results of this study speak to the potential of automated EoV shoreline monitoring through segmentation and classification tree approach, which would reduce down data processing and analysis time. With the growing constellation of high and medium spatial resolution satellite-based sensors and the development of semi or fully automated image processing technology, it is now possible to remotely assess the short and medium-term shoreline dynamics on dynamic atolls. Landsat estimates were reasonably matched to those derived from fine resolution imagery, with some caveats about island size and shape.
“The new study shows that a collapse of Larsen C would result in inland ice discharging about 4 mm to sea level, while the response of glaciers to George VI collapse could contribute over five times more to global sea levels, around 22 mm.” click here
“Let’s start with the automatic assumption by the public and the media that any major environmental issue, like global warming, glaciers melting, or sea level rising, is due to human activity. It reflects that bias, but also how little they know about all the natural causes of change. The simple assumption is that sea level rise is due to anthropogenic global warming (AGW) causing increased melting of glaciers adding more water to the oceans. In reality, just as with climate change, there is a multitude of causes, and few people know very little about any of them, and even those that do know have a quite limited understanding. “ click here
Posted in Sea Level
Tagged sea level
“Within Australian universities, from Murry Shelby to Bob Carter, from Peter Ridd to myself, academics not supporting the narrative are simply forced to leave, in a way or another, or not even start, as Bjorn Lomborg. I do not believe anyone within Australian universities will declare that the sea levels in Fremantle have been rising since 1897 without any significant acceleration component, and in the next 8 years they may rise on average of not even 25 millimetres, but 16 millimetres …..” click here
“Since publishing my last two posts here and here on the Church and White (“C&W”) 2011 sea level dataset, some folks have queried why I didn’t use the Church and White 2013 dataset instead. The answer is simple. It’s because of the hockeystick.
What hockeystick, you might ask? Why, the C&W hockeystick … the figure below shows the difference between the C&W 2013 and the C&W 2011 data.” click here